Textile spinning machines are provided with a large number of bobbin spindle which are mounted on a spindle rail which usually extends along opposing sides of the spinning frame machine and may comprise as many as 200 individual spindles. Associated with each spindle is a bobbin which is received over the spindle. Yarn or other textile fibers are wound on the bobbin which, when full, is then removed from the spindle to be replaced by an empty bobbin.
Doffing is the art of removing the yarn filled bobbins from the spindle and replacing them with an empty bobbin. This is often done manually by a skilled laborer with his hands. Prior devices have been developed for removing a plurality of yarn filled bobbins simultaneously from the spinning rail such as shown in U.S. Pat. No. 3,462,934 wherein an elongated inflatable bag member is inserted into the interior of a top end of the bobbin. The bag member is then inflated to grip the bobbin for removal from the spindle. However, such a device requires a source of pressure for inflating the elastomeric bag member and the conveying of fluid pressure from the source to the bag which can result in a rather complex and costly system.
Another prior device for automatically doffing and transporting full bobbins from spindles is disclosed in U.S. Pat. No. 3,132,463 wherein a plurality of bobbin grippers are provided for gripping around a recessed portion formed in the top of the bobbin. The bobbin gripping means are carried on an endless chain running over the spindles of the spinning frame carried by a vertically and horizontally movable frame.
U.S. Pat. No. 3,686,847 discloses a later developed device which also utilizes an endless belt having a plurality of bobbin gripping devices for automatically removing and replacing bobbins in a spindle type spinning machine.
The alignment of the bobbin gripping device with the bobbin itself is a problem to which considerable attention must be given in the prior known devices. Once a yarn filled bobbin is missed by the automatic engaging device, the automatic doffing appartus must be stopped and the missed bobbin must be removed manually. This results in loss of operating time. The automatic doffing or removal of the yarn filled bobbin usually involves removing a very large number of bobbins at one time. To avoid missing a bobbin requires aligning of the bobbin gripping device with the bobbin in a highly accurate and reliable manner.